Sterilization processing of retorted products having contents such as a liquid food and the like sealed in a packaging bag made of a heat-resistant resin film and the like is carried out by heating the packaging bag in a retort with steam or hot water. However, in the case of sterilization processing of retorted products having a large or thick packaging bag, or having highly viscous contents or containing solid products, heat transfer inside the retort during heating is poor, thereby requiring a long period of time for the product temperature in the center to reach a set temperature, while conversely causing burning or scorching of the contents as a result of the product temperature rising quickly at portions close to the surface of the bag thereby exposing the contents to a high temperature for an extended period of time.
Therefore, in order to solve these problems, the present applicant proposed a sterilizing method and apparatus for sterilizing retort foods in a retort while sliding to the front and back and to the left and right followed by cooling (see Patent Document 1). As shown in FIG. 12, a sterilizing apparatus for carrying out this sterilizing method has a carriage A4 supported by means of wheels A3 on a support table A2 such as a tray provided within a retort body A1, and trays A6, housing a large number of retort foods A5 arranged in a row, are supported by being stacked in multiple layers on the carriage A4.
The carriage A4 is coupled to a driveshaft A9 of a cranking mechanism A8 driven by a motor A7 through a shaft sealing mechanism A10 provided in the retort body A1, and when the motor A7 is driven and rotated, the driveshaft A9 reciprocates in the lengthwise direction of the retort body A1 in conjunction therewith, and the carriage A4 coupled to the driveshaft A9 slides forward and backward in the lengthwise direction of the retort body A1 within the retort body A1 together with the trays A6.
Patent Document 1: Japanese Patent Publication No. S58-2666
However, in the sterilizing apparatus described in Patent Document 1 above, since the motor and cranking mechanism that drive the carriage are provided in close proximity to one end in the lengthwise direction of the retort body, loading and unloading of trays to and from the retort body can only be carried out from the other end, and unidirectional transfer of retort foods in the manner of loading trays housing unprocessed retort foods from one end of the retort body while unloading trays from the other end following completion of sterilization cannot be carried out, thereby placing limitations on the configuration of the retort food production line. In addition, although the driveshaft of the cranking mechanism is coupled to the carriage inside the retort body through the shaft sealing mechanism provided in the retort body, since the shaft sealing mechanism employs a structure in which the driveshaft is sealed by making sliding contact with the driveshaft reciprocating in the axial direction, this shaft sealing mechanism had problems such as the shaft sealing mechanism for maintaining sealing performance being complex. In addition, since the driveshaft of the cranking mechanism during motor rotation reciprocates forward and backward in the axial direction thereof, it was necessary to provide space for the forward and backward stroke of the driveshaft in close proximity to the retort body.